1. Field of the Invention
The present invention relates to a process for producing quinazolone derivatives which are useful as pigments and electrophotographic pigments.
2. Description of the Prior Art
7,15-Dihydropyrido[2,1-b]pyrido[1',2':1,2]pyrimido[4,5-g]quinazoline-7,15-d ione and derivatives thereof are useful as organic red pigment and electrophotographic pigment.
It has been known to produce the compounds by heating 6,7,14,15-tetrahydropyrido[2,1-b]pyrido[1',2':1,2]pyrimido[4,5-g]quinazoli ne-7,15-dione and derivatives thereof in nitrobenzene, glacial acetic acid and piperidine (U.S. Pat. No. 3,888,665).
The inventors have previously invented an improved process for producing the former compounds in which the later compounds were reacted in alkaline conditions (Japanese Unexamined Patent Publication No. 42724/1976). In the improved process, the reaction is carried out in an alkaline condition whereby a ring-opened compound is produced. In order to convert the compound to the object product, it is necessary to acidify the reaction mixture after the reaction for the recycliation, whereby the operation is complicated. Also, it has been necessary to use an expensive organic solvent.